A grinding machine for generating an epitrochoidal surface on a work

ABSTRACT

A grinding machine for generating an epitrochoidal surface includes a rotating sleeve which rotatably carries a work spindle with a given eccentricity with respect thereto. The sleeve is mounted on a work head adapted for pivotable motion about the grinding point of a grinding tool rotatably carried by a tool rest to which is imparted a feeding motion. An epicyclic gearing is provided to transmit rotative power to the work spindle when the sleeve is connected with a drive means, and comprises two pairs of meshing gears, of which two are coaxially mounted on a shaft carried by the sleeve for meshing engagement with another gear secured to one end of the work spindle and a further gear secured to the work head in concentric relationship with the sleeve.

United States Patent 1191 Asano et a1.

GRINDING MACHINE FOR G NE ING, AN EPITROCHOIDAL SURFACE ON A WORK Inventors: I-liroaki Asano, Chiryu; Kazuhiro Sakane, Kariya, both of Japan Assignee: Toyoda Koki Kabushiki Kaisha,

Kariya-shi, Aichi-ken, Japan Filed: Mar. 12, 1973 i Appl. N0.: 340,101

Foreign Application Priority Data Mar. 21, 1972 Japan 47-33220[U] us. (:1. 51/46, 51/50 R, 51/97 NC, 51/D1G. 32

Int. Cl B24b 5/16 Field 61 Search 51/46, 50 R, 97 R, 97 NC, 51/010. 32; 82/1.3; 408/54; 74/440 References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS 1,239,213 4/1967 Germany 51/95 R 1,117,569 6/1968 Great Britain 51/95 R Primary Examiner-Al Lawrence Smith Assistant Examiner-Nicholas P. Godici Attorney, Agent, or Firm-Wenderoth, Lind & Ponack ABSTRACT A grinding machine for generating an epitrochoidal surface includes a rotating sleeve which rotatably carries a work spindle with a given eccentricity with respect thereto. The sleeve is mounted on a work head adapted for pivotable motion about the grinding point of a grinding tool rotatably carried by a tool rest to which is imparted a feeding motion. An epicyclic gearing is provided to transmit rotative power to the work spindle when the sleeve is connected with a drive means, and comprises two pairs of meshing gears, of which two are coaxially mounted on a shaft carried by the sleeve for meshing engagement with another gear secured to one end of the work spindle and a further gear secured to the work head in concentric relationship with the sleeve.

6 Claims, 3 Drawing Figures PATENIED 1 I974 3. 857. 203

sum 1 0r 5 F/Gi/ PATENTED DECS 1 I974 SHEET 2 BF 3 m mzk PATENTED 1 I974 SHEET 3 BF 3 GRINDING MACHINE FOR, GENERATING AN EPITROCHOIDAL SURFACEON A WORK BACKGROUND OF THE INVENTION The invention relates to a grinding machine for generating an epitrochoidal surface, and more particularly to such a grinding machine having an enhanced grinding capability achieved by increasing the strength of the gearing which controls the work spindle and the rate of revolution thereof around the axis of a sleeve relative to the rate of rotation thereof on the axis thereof involved in the generation of an epitrochoidal surface.

Generally, a gearing for generating an epitrochoidal surface often comprises an internal gear and a pinion meshing therewith. However, because the amount of eccentricity as well as the rate of rotation relative to the rate of revolution are restricted in an epitrocoid generating motion, it follows that with the internal gear and pinion arrangement, the diameters of the respective gears become uniquely fixed for a given amount of eccentricity. Specifically, the internal gear and pinion should have a gear ratio of 3:2, and the difference in the radius of the two gears should be equal to the eccentricity to produce a required epitrochoidal surface on the workpiece. Thusdenoting the eccentricity by e, the pitch circles of the internal gear and the pinion have diameters which are represented by 62 and 4e, respectively. This restriction on the diameter of the two gears prevents a greater module from being achieved,

with consequent insufficient strength of the gears SUMMARY OF THE INVENTION Therefore, it is an object of theinven tion to provide a grinding machine for generating an epitrochoidal surface which meets the above need.

In accordance with the invention, the grinding machine for generating an epitrochoidal surface includes a rotating sleeve which rotatably carries, with a given eccentricity, a work spindle on which is placed a work. The rotating sleeve is mounted on a work head, which is arranged for pivotable motion about the grinding point of a grinding tool rotatably carried by a tool rest to which is imparted a feeding motion. A first gear is secured to the pivotable work head in concentric relationship with the rotating sleeve; a second gear is secured to one end of the work spindle; and third and fourth gears meshing with the first and second gears, respectively, are fixedly mounted on a support shaft in coaxial relationship with each other. The rotating sleeve is connected with a drive means for imparting to the work spindle a given rate of rotation with respect to its revolution through the gears.

BRIEF DESCRIPTION OF DRAWINGS For a better understanding of the invention, an embodiment thereof will be described with reference to the drawings, in which:

FIG. 1 is a front view of one embodiment of the grinding machine according to the invention,

FIG. 2 is a longitudinal section, on an enlarged scale, of the work head, and

FIG. 3 is a cross-section taken along the line III lll shown in FIG. 2.

Referring initially to FIGS. 1 and 2, the grinding machine is generally shown to include a bed 1, work head 2, work table 3, column 4, saddle 5, tool rest 6, wheel spindle stock 7, grinding wheel 8 and wheel truing device 9. The work head 2 is slidably mounted on a sliding surface 10 formed on top of the bed 1, and is pivotable about a pivot 20, the axis of which is aligned with the grinding point P of the grinding wheel 8 so that the work head 2 is pivotable about the grinding point P. The work table 3 is secured to a work spindle 11 which is inturn rotatably carried by a rotating sleeve 12. The axis 70 of the spindle 11 is eccentric with respect to the axis 71 of the sleeve 12 by an amount e, so that an epitrochoid generating motion is imparted to a work W, placed on the work table 3, in terms of revolution and rotation when the rotating sleeve 12 and the work spindle 11 are driven by a drive mechanism to be described later. A pivoting motion of the work head 2 is produced in association with the generating motion and is transmitted to the work W through the work head 2. Such a pivoting motion is controlled in such a manner that the line extending through the grinding point P of the grinding wheel 8 and the center of the grinding wheel is maintained normal to the epitrochoidal surface to be produced. The tool rest 6 is oscillated by an oscillation mechanism, not shown, along the guide ways 5a of the saddle 5 in the axial direction of the grinding wheel. The saddle 5 is moved by a feeding mechanism, not shown, along the horizontally extending guide ways 4a formed in the front side of the column 4 for feeding the grinding wheel 8 toward the work W in a direction normal to the epitrochoidal surface on the word W. The wheel truing device 9 is mounted on the tool rest 6 and carries a diamond tool 9a which is adapted to slide vertically with respect to the grinding wheel 8 for dressing it. The compensation for the dressing operation is performed by shifting thesaddle 5 through an amount of the dressing operation so that the grinding surface of the grinding wheel 8 is maintained at a fixed position with respect to the work W.

Referring to FIG. 2 more specifically, the center of pivoting motion of the work head 2 isdefined by the pivot 20 that is fixedly mounted on the bed 1. As indicated, the lower surface of the work head 2 is in sliding contact with and guided by the guide surface 10 on top of the bed 1. The rotating sleeve 12, journalled in the work head 2, is formed with a bore 12a which is eccentric with respect to the axis 71 of the sleeve and in which the work spindle 11 is rotatably carried by means of bearings 21 and 22. At its lower end, the rotating sleeve 12 is formed with an enlarged bore 12b in which is received an epicyclic gearing 23. The epicyclic gearing 23 comprises four gears 31, 32, 33 and 34, which are arranged as follows; a first gear 31 is secured, in concentric relationship with the rotating sleeve 12, to a holder 24 that is fixedly mounted on the bottom of the work head 2; a second gear 34 is secured to the lower end of the work spindle 11; and third and fourth gears 32 and 33 meshing with the first and second gears 31 and 34, respectively, are coaxially mounted on a common shaft 35 which is rotatably carried by a retaining member 36 and a support shaft 37 both secured to the rotating sleeve 12.

The respective number of teeth Z,, Z Z and Z, on these gears 31 to 34 for the work spindle l1 and the amount of eccentricity e is in a relationship as represented by the following equation:

8 (Z; +.Z4)/ 1 2)/ l (l) where m denotes the module of the gears. Denoting the number of revolutions of the rotating sleeve 12 and the work spindle 11 by No and N, respectively, the generation of an epitrochoidal surface requires that N/No /2, the negative sign indicating the opposite directions of rotation. Thus the gear ratio is given by the following equation:

This means that the size and module of the respective gears can be arbitrarily chosen independently of the magnitude of the eccentricity e, and hence the strength of the gears is increased, provided the gearing chosen satisfies the gear ratio requirements imposed by the equations (1) and (2).

Each of the gears 31 and 34 is constituted by a pair of gears having an identical circular pitch, 31a, 31b or 34a, 34b. The gears of each pair are in sliding contact with each other and supported to permit their relative rotation. A spring 310 or 34c having a relatively high.

spring constant is interposed between the gears of each pair to urge them againsteach other. Accordingly, the gears of each pair are angularly shifted relative to each other by the amount of backlash so as to eliminate the backlashexisting between the gears 31 and 32 and between the gears 33 and 34. This kind of technology is rather conventional and is described for example, in U.S. Pat. No. 3,648,534.

The rotating sleeve 12 has fixedly mounted thereon a worm gear 40 which meshes with a worm 41 which is in turn carried by a shaft 58 rotatably journalled in the work head 2. At its one end, the shaft 58 carries a bevel gear 59 which meshes with another bevel gear 42 rotatably carried by the.work head 2. The shaft on which the bevel gear 42 is mounted has at itsother end a gear 43 fixedly mounted thereon, which meshes with a gear 44 on a gear shaft 45 which is in turn rotatably carried by the bed 1 in concentric relationship with the pivot 20. The gear shaft 45 carries a bevel gear 46 which meshes with another bevel gear 47 connected with a drive means not shown. The described arrangement imparts a rotative drive to 'the work spindle 11 and the rotating sleeve 12 on the work head 2. In one end of the work head 2 is journalled a rotary shaft 51 having a crank arm 50 secured atits upper end, the shaft 51 also having a worm gear 52 fixedly mounted thereon. The worm gear 52 meshes with a worm 60 which is in turn connected by way of a shaft 61, journalled in the work head 2, with a bevel gear 53 which meshes with the bevel gear 42. The crank arm 50 carries a crank pin 54 at its end, which rotatably carries a slider 55. The slider 55 is received and guided by a rectilinear guide groove 57 formed in a guide block 56 so as to extend parallel to the direction of the slide motion of the tool rest 6 along the guide ways 4a, the block 56 being secured to the bed 1. As a result, when the crank arm 50 is driven for rotation from the single drive source through the gearing 47, 46, 44, 43, 42, 53 and 52, the work head 2 is subjected to pivoting about the pivot 20, so that when the saddle 5 is fed along the guide ways 4a, the grinding wheel 8 is fed in a direction normal to the epitrochoidal surface in cooperation with the epitrochoid generating motion which is imparted by therevolution and rotation of the work spindle ll.

When a work W is mounted on the work table 3, the tool rest 6 is moved down along the guide way 5a on the saddle 5 and is oscillated in a vertical direction.

At the same time, the gear'47 is driven by the drive source and thus, the sleeve 12 is rotated through the gearing 47, 46, 44, 43, 42, 59 and 41. Since the gear 31 is fixedly mounted on the workhead 2, the spindle 11 is also rotated in adirection opposite to the rotation of the sleeve 12. Since the axes of the spindle 11 and the sleeve 12 are eccentric to each other by the eccentricity e, the spindle 11 is rotated around its axis and is also revolved around the axis of the sleeve 12 at the radius e. Accordingly, the grinding wheel 8 the peripheral edge of which is aligned with the axis of the pivot 20 can create an epitrochoidal surface on the work. Of course, while the work W is rotated on the work table 3, the saddle 5 and the grinding wheel 8 are fed toward the work W by the feeding mechanism in order to obtain the required size of the epitrochoidal surface thereon.

When the gear 47 is rotated by the drive source, the rotary shaft 51 is rotated through the gearing 47, 46, 44, 43, 42, 53 and 52. Therefore, the crank arm is rotated and thus, the slider is caused to slide along the guide groove 57 so that the workhead 2 is pivotable moved around the pivot 20. As mentioned above, since this pivotal motion is performed in coordination with the epitrochoid generating motion, the line normal to the epitrochoidal surface at the grinding point is always parallel with the guide ways 4a and the grinding wheel 8 can be, therefore, fed in a direction normal to the epitrochoidal surface.

From the foregoing, it will be appreciated that the use of a pair of coaxial gears for meshing engagement with another pair of gears which are located at the center of revolution and at the center of rotation, respectively, as a gearing for transmission of rotation to the work spindle l1 journalled eccentrically with respect to the rotating sleeve 12 permits an arbitrary choice of the number of teeth and the module of the respective gears while satisfying the given eccentricity and gear ratio requirements. This enables the strength of the gears to be increased independently of the amount of the eccentricity, with the consequence that the rigidity of the epitrochoidal surface grinding machine as will as its working accuracy and capability can be greatly enhanced.

What is claimed is:

1. In a grinding machine for generating an epitrochoidal surface including a rotating sleeve which rotatably carries a work spindle at a given eccentricity with respect to the rotating sleeve, said rotating sleeve being mounted on a work head and adapted for a pivotal motion about the grinding point of a grinding tool rotatably carried by a tool rest to which is imparted a feeding motion, and a drive means to which said rotating sleeve is connected, the improvement comprising a first gear secured to the pivotable work head in concentric relationship with the rotating sleeve, a second gear secured to one end of the work spindle, third and fourth gears meshing with the first and second gears, respectively, and a support shaft rotatably carried by the rotating sleeve and on which said third and fourth gears are fixedly mounted in coaxial relationship with each other, whereby the work spindle is rotated at a given rate of rotation relative to the revolution of the sleeve through the first to fourth gears.

2. A grinding machine for generating an epitrochoidal surface of a work comprising:

a bed,

a work head mounted on said bed and a pivot provided on said bed around which said work head is pivotable,

a tool rest having a tool for performing a machining operation on the work,

a sleeve rotatably mounted on said work head and a drive means coupled to said sleeve for rotating it,

a work spindle rotatably mounted on said rotatable sleeve at a given eccentricity with respect thereto,

a first spur gear fixedly mounted on said work head in concentric relation with respect to said rotatable sleeve,

21 second spur gear concentrically mounted on said spindle, and

third and fourth spur gears rigidly connected to each other for rotation rogether and rotatably mounted on said sleeve and meshingly engaged with said first and second gears, respectively. 3. A machine tool according to claim 2, wherein the number of teeth on said first, second, third and fourth gears are determined by the equation where;

Z, number of teeth of the first gear Z number of teeth of the fourth gear Z, number of teeth of the third gear Z number of teeth of the second gear m module of the gears e the eccentricity between the axes of the sleeve and work spindle.

4. A grinding machine according to claim 3, wherein said third and fourth gears are concentric with each other.

5. A grinding machine according to claim 2, which further comprises a crank arm mechanism connected to said drive means and said work head for pivoting said work head around said pivot.

6. A grinding machine according to claim 2, wherein the peripheral edge of said tool is aligned with the axis of said pivot. 

1. In a grinding machine for generating an epitrochoidal surface including a rotating sleeve which rotatably carries a work spindle at a given eccentricity with respect to the rotating sleeve, said rotating sleeve being mounted on a work head and adapted for a pivotal motion about the grinding point of a grinding tool rotatably carried by a tool rest to which is imparted a feeding motion, and a drive means to which said rotating sleeve is connected, the improvement comprising a first gear secured to the pivotable work head in concentric relationship with the rotating sleeve, a second gear secured to one end of the work spindle, third and fourth gears meshing with the first and second gears, respectively, and a support shaft rotatably carried by the rotating sleeve and on which said third and fourth gears are fixedly mounted in coaxial relationship with each other, whereby the work spindle is rotated at a given rate of rotation relative to the revolution of the sleeve through the first to fourth gears.
 2. A grinding machine for generating an epitrochoidal surface of a work comprising: a bed, a work head mounted on said bed and a pivot provided on said bed around which said work head is pivotable, a tool rest having a tOol for performing a machining operation on the work, a sleeve rotatably mounted on said work head and a drive means coupled to said sleeve for rotating it, a work spindle rotatably mounted on said rotatable sleeve at a given eccentricity with respect thereto, a first spur gear fixedly mounted on said work head in concentric relation with respect to said rotatable sleeve, a second spur gear concentrically mounted on said spindle, and third and fourth spur gears rigidly connected to each other for rotation rogether and rotatably mounted on said sleeve and meshingly engaged with said first and second gears, respectively.
 3. A machine tool according to claim 2, wherein the number of teeth on said first, second, third and fourth gears are determined by the equation (Z1/Z2) . (Z3/Z4) 3/2 and e (m(Z3+ Z4)/2) - (m(Z1 + Z2)/2) where; Z1 number of teeth of the first gear Z2 number of teeth of the fourth gear Z3 number of teeth of the third gear Z4 number of teeth of the second gear m module of the gears e the eccentricity between the axes of the sleeve and work spindle.
 4. A grinding machine according to claim 3, wherein said third and fourth gears are concentric with each other.
 5. A grinding machine according to claim 2, which further comprises a crank arm mechanism connected to said drive means and said work head for pivoting said work head around said pivot.
 6. A grinding machine according to claim 2, wherein the peripheral edge of said tool is aligned with the axis of said pivot. 